Sound Level Distance Calculator
Project free-field point-source sound pressure level between two distances and inspect the inverse-square distance curve.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Convert both distances to the same unit and apply spherical free-field spreading for a point source. The pressure ratio changes inversely with distance, giving a 20-logarithm sound-pressure-level change.
L₂=L₁+20 log₁₀(d₁/d₂)
Worked example
A point source measured at 90 dB at 1 m is predicted as about 77.9588 dB at 4 m. Each distance doubling subtracts about 6.0206 dB.
Assumptions and input details
This is only the geometric free-field point-source model. Distances must be positive. The entered level may be weighted or unweighted, but the same measurement convention must be kept. Reflections, ground, air absorption, barriers, directivity, multiple sources, near-field behavior and hearing-risk exposure duration are excluded. Do not use this arithmetic as a workplace compliance determination.
References: OSHA Technical Manual: free-field distance equation
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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